Semiconductor laser device

ABSTRACT

A semiconductor laser device includes a base; a heat sink protruding upward from the base and including an upper surface and a lateral surface extending from the base to the upper surface; a plurality of lead electrodes separated from the heat sink; a submount including: a first main surface fixed to the lateral surface of the heat sink, and a second main surface including a first fixing part, an upper second fixing part, and a lower second fixing part; a protective element fixed to the upper second fixing part; and a wire connecting the protective element and one of the plurality of lead electrodes.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 15/433,368, filed on Feb. 15, 2017, which claims priority toJapanese Patent Application No. 2016-027113, filed on Feb. 16, 2016, thedisclosure of which is hereby incorporated by reference in its entirety

BACKGROUND

The present disclosure relates to a semiconductor laser device.

A semiconductor laser device includes a semiconductor laser element, aprotective element and a submount on which the semiconductor laserelement and the protective element are fixed, as described in, forexample, Japanese Patent No. 5659876. The submount includes a fixingpart on which the semiconductor laser element is fixed, and a fixingpart on which the protective element is fixed. The position of each ofthe fixing parts on the submount is previously determined in accordancewith the position where an optical waveguide region of the semiconductorlaser element is formed.

Normally, semiconductor laser elements of one type are obtained from asingle piece of wafer. In some cases, semiconductor laser elementsdiffering from each other in the formation position of the opticalwaveguide region are obtained from a single piece of wafer, as describedin, for example, Japanese Unexamined Patent Publication No. 2009-200341.

SUMMARY

With a semiconductor laser device in which the semiconductor laserelement provided with an optical waveguide region around its center isdisposed around the center of the submount, aligning the submount withanother member of the semiconductor laser device substantially alignsthe light output part of the semiconductor laser element with that othermember.

However, a change in the position of the optical waveguide region on thesemiconductor laser element changes the position on the submount wherethe semiconductor laser element is fixed, unless any change is made inthe disposition position of the submount to which the semiconductorlaser element is fixed. In accordance therewith, the position on thesubmount where the protective element is fixed also changes. The fixingpart on the submount to which the semiconductor laser element or theprotective element is fixed is a metal layer obtained from patterning orthe like. Accordingly, in the case where the position on the submountwhere the semiconductor laser element or the protective element is fixedis to be changed, a submount of different type, that is, a submounthaving the fixing part at the position corresponding to the change isused.

However, as disclosed in JP 2009-200341 A, for example, in the case inwhich a plurality of semiconductor laser elements differing from eachother in the formation position of the optical waveguide region isobtained from a single piece of wafer, providing a submountcorresponding to the difference in the formation position necessitatesusing a submount of a plurality of types. Such an increase in the numberof types of the submount may disadvantageously make inventory control ofthe submount troublesome.

The problem described above may be solved by certain embodiments of thepresent invention.

In one embodiment, a semiconductor laser device includes a base; a heatsink protruding upward from the base and including an upper surface anda lateral surface extending from the base to the upper surface; aplurality of lead electrodes separated from the heat sink; a submountincluding: a first main surface fixed to the lateral surface of the heatsink, and a second main surface having an upper half region and a lowerhalf region, an upper edge, a lower edge, and a first lateral edgeextending from the upper edge to the lower edge, the second main surfaceincluding a first fixing part, an upper second fixing part, and a lowersecond fixing part, wherein the upper second fixing part is disposedbetween the first fixing part and the first lateral edge in the upperhalf region, and the lower second fixing part is disposed between thefirst fixing part and the first lateral edge in the lower half region; asemiconductor laser element including: a light output surface, a lightreflecting surface, a first lateral surface, a second lateral surfaceopposite the first lateral surface, a fixing surface that is fixed tothe first fixing part, a wire connecting surface opposite the fixingsurface, and an optical waveguide region, wherein the optical waveguideregion is disposed closer to the first lateral surface than the secondlateral surface, wherein the fixing surface is fixed to the first fixingpart such that the light output surface is directed upward and theoptical waveguide region is disposed on or around an area between amidpoint of the upper edge and a midpoint of the lower edge of thesecond main surface as seen in a front view; a protective element fixedto the upper second fixing part; and a wire connecting the protectiveelement and one of the plurality of lead electrodes.

In another embodiment, a semiconductor laser device includes a housingincluding: an insulating part, a plurality of wiring parts, and a recessdefined by a bottom surface and inner lateral surfaces surrounding thebottom surface, wherein the wiring parts are partially exposed from theinsulating part at the recess; a submount including: a first mainsurface fixed to the bottom surface of the recess, a second main surfacehaving a front half region and a rear half region, a front edge, a rearedge, and a first lateral edge extending from the front edge to the rearedge, the second main surface including a first fixing part, a frontsecond fixing part, and a rear second fixing part, wherein the frontsecond fixing part is disposed between the first fixing part and thefirst lateral edge in the front half region, and the rear second fixingpart is disposed between the first fixing part and the first lateraledge in the rear half region; a semiconductor laser element including: alight output surface, a light reflecting surface, a first lateralsurface, a second lateral surface opposite the first lateral surface, afixing surface that is fixed to the first fixing part, and a wireconnecting surface opposite the fixing surface, and an optical waveguideregion, wherein the optical waveguide region is disposed closer to thefirst lateral surface than the second lateral surface, wherein thefixing surface is fixed to the first fixing part such that the lightoutput surface is directed frontward and the optical waveguide region isdisposed on or around an area between a midpoint of the front edge and amidpoint of the rear edge of the second main surface as seen in a topview; a protective element fixed to the front second fixing part; and awire connecting the protective element and one of the plurality ofwiring parts.

With the above-described semiconductor laser device, the submount of asingle type in which the fixing part is formed at a unique position canbe used for both the semiconductor laser elements differing from eachother in the position of the optical waveguide region. This prevents anincrease in the number of types of the submount, making the inventorycontrol less troublesome.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic front view of a semiconductor laser deviceaccording to a first embodiment.

FIG. 1B is a schematic front view of the semiconductor laser deviceaccording to the first embodiment (in which a cap is not shown).

FIG. 1C is an enlarged view of a portion surrounded by a broken line inFIG. 1B.

FIG. 1D is a schematic rear view of the semiconductor laser deviceaccording to the first embodiment.

FIG. 1E is a schematic plan view of the semiconductor laser deviceaccording to the first embodiment.

FIG. 1F is a schematic plan view of the semiconductor laser deviceaccording to the first embodiment (in which the cap is not shown).

FIG. 1G is an enlarged view of a portion surrounded by a broken line inFIG. 1F.

FIG. 1H is a schematic front view of a submount according to the firstembodiment.

FIG. 2A is a schematic front view of a semiconductor laser deviceaccording to a second embodiment (in which a cap is not shown).

FIG. 2B is an enlarged view of a portion surrounded by a broken line inFIG. 2A.

FIG. 2C is a schematic front view of a submount according to the secondembodiment.

FIG. 3A is a schematic side view showing the positional relationshipbetween the semiconductor laser element and a collet.

FIG. 3B is an enlarged view of a portion surrounded by a broken line inFIG. 3A.

FIG. 4A is a schematic side view showing the positional relationshipbetween a protective element and the collet.

FIG. 4B is an enlarged view of a portion surrounded by a broken line inFIG. 4A.

FIG. 5A is a schematic top view of a semiconductor laser deviceaccording to a third embodiment (in which a cap is not shown).

FIG. 5B is a schematic cross-sectional view taken along line 5B-5B inFIG. 5A.

FIG. 5C is a schematic cross-sectional view taken along line 5C-5C inFIG. 5A.

FIG. 5D is an enlarged view of a portion surrounded by a broken line inFIG. 5A.

DETAILED DESCRIPTION Semiconductor Laser Device 1 According to FirstEmbodiment

FIGS. 1A, 1B, and 1C are a schematic front view of a semiconductor laserdevice 1 according to the first embodiment, a schematic front view (inwhich a cap is not shown) thereof, and an enlarged view of a portionsurrounded by a broken line in FIG. 1B, respectively. FIGS. 1D, 1E, 1F,and 1G are a schematic rear view of the semiconductor laser device 1, aschematic plan view thereof, a schematic plan view (in which the cap isnot shown) thereof, and an enlarged view of a portion surrounded by abroken line in FIG. 1F, respectively. FIG. 1H is a schematic front viewof a submount 40 according to the first embodiment. For ease ofunderstanding, FIG. 1A illustrates each member covered with a cap 80with a broken line, showing each member through the cap 80.

As shown in FIGS. 1A to 1H, the semiconductor laser device 1 includes: abase 10; a heat sink 20 disposed above the base 10; a plurality of leadelectrodes 31, 32 disposed laterally relative to the heat sink 20; asubmount 40 including a first main surface 41 and a second main surface42, the first main surface 41 being fixed to a lateral surface of theheat sink 20, the second main surface 42 including a first fixing part43 and two second fixing parts 44 a, 44 b disposed laterally relative tothe first fixing part 43 and respectively in an upper half region and alower half region of the second main surface 42; a semiconductor laserelement 50 including a light output surface 51, a light reflectingsurface 52, two lateral surfaces 53, 54 intersecting the light outputsurface 51, and an optical waveguide region 55 formed to be offsettoward one of the two lateral surfaces 53, 54, the semiconductor laserelement 50 being fixed to the first fixing part 43 so that the lightoutput surface 51 is directed upward and the optical waveguide region 55is disposed on or around a line A that passes through the midpoint ofthe upper edge and the midpoint of the lower edge of the second mainsurface 42 as seen in a front view; a protective element 60 fixed toupper one of the two second fixing parts 44 a, 44 b; and a wire 70connecting between the protective element 60 and one of the plurality oflead electrodes 31, 32. In the following, a detailed description isgiven.

(Base 10)

Preferably, the base 10 is made of a material exhibiting relatively highthermal conductivity, e.g., about 20 W/mK or greater, so that heatgenerated at the semiconductor laser element 50 is efficiently releasedto the outside. Specifically, use of metal such as Cu, Al, Fe, Ni, Mo,CuW, CuMo or the like is preferable.

Exemplary shapes of the base 10 as seen in a plan view include a circle,an ellipse, a polygon such as a quadrangle, and any shape similar to theforegoing. More specifically, for example a circular and flat memberhaving a diameter of about 3 mm to 10 mm may be employed as the base 10.Preferably, the thickness of the base 10 is, for example, about 0.5 mmto 5 mm.

(Heat Sink 20)

The heat sink 20 may be made of the material identical to that of thebase 10, or may be made of a different material. For example, as thematerial of the base 10, iron alloy may be employed for welding the cap80, and copper or copper alloy being excellent in heat releasingproperty may be employed as the material of the heat sink 20. Thus, theheat sink 20 can efficiently release heat from the semiconductor laserelement 50. The heat sink 20 is at least partially disposed above thebase 10. The base 10 and the heat sink 20 may be made of separatemembers, or they may be parts of a single member. In the presentembodiment, a member structured by the base 10 and the heat sink 20serves as the stem.

(Plurality of Lead Electrodes 31, 32)

The lead electrodes 31, 32 are members for connecting the semiconductorlaser element 50 to the external power supply. An electricallyconductive material is employed for the lead electrodes 31, 32. The leadelectrodes 31, 32 are, for example, rod-like members made of metal. Thelead electrodes 31, 32 are, for example, disposed so as to penetratethrough holes provided at the base 10, and bonded to the base 10 withlow melting point glass or the like. The lead electrodes 31, 32 aredisposed laterally relative to the heat sink 20. In the presentembodiment, as shown in FIG. 1F, the lead electrodes 31, 32 are disposedat positions on the front side of the heat sink 20 and being spacedapart from the heat sink 20. Such a disposition is also referred to as“disposed laterally relative to the heat sink 20”.

(Submount 40)

The submount 40 is preferably made of a material that shows a smallerdifference in thermal expansion coefficient from the semiconductor laserelement 50 than the base 10 and the heat sink 20 do, so as to preventthe semiconductor laser element 50 from coming off. Further, thesubmount 40 is preferably made of a material that exhibits high thermalconductivity so as to be capable of efficiently releasing heat generatedat the semiconductor laser element 50. Specifically, AlN, CuW, diamond,SiC, ceramic or the like may be preferably employed as the submount 40.

The submount 40 includes the first main surface 41 and the second mainsurface 42. The first main surface 41 can be fixed to the lateralsurface of the heat sink 20 with Au bumps, Au nanoparticles, Agnanoparticles, AuSn solder, a solder paste member and the like. Whilethe submount 40 and the heat sink 20 may be in direct contact with eachother, other member may be interposed between the submount 40 and theheat sink 20.

The second main surface 42 includes the first fixing part 43 and thesecond fixing parts 44 a, 44 b. The semiconductor laser element 50 isfixed to the first fixing part 43, and the protective element 60 isfixed to one of the two second fixing parts 44 a, 44 b.

The first fixing part 43 and the second fixing parts 44 a, 44 b arepreferably made of a metal material, for example, and particularlypreferably have an adhesive layer which is molten by being heated andwith which the semiconductor laser element 50 and the like are bonded.Thus, the semiconductor laser element 50 and the like can be surelyfixed to the first fixing part 43 and the second fixing parts 44 a, 44b. For example, when the first fixing part 43 and the second fixingparts 44 a, 44 b are Pt/AuSn/Au, AuSn serves as the adhesive layer, andPt and Au serve as cover layers that cover the adhesive layer. Notethat, in the present embodiment, the first fixing part 43 and the secondfixing parts 44 a, 44 b are entirely structured by the adhesive layer(e.g., AuSn).

The first fixing part 43 is disposed to be positioned on the line A thatpasses through the midpoint of the upper edge and the midpoint of thelower edge of the second main surface 42 as seen in a front view.Further, the first fixing part 43 is disposed such that the opticalwaveguide region 55 of the semiconductor laser element 50 is positionedon or around the line A. Thus, aligning the submount 40 with the heatsink 20 such that the line A of the submount 40 matches with the linethat passes through the midpoint of the upper edge and the midpoint ofthe lower edge of the heat sink 20 aligns the light output part of thesemiconductor laser element 50 (the end of the optical waveguide region55 on the light output surface 51 side) with the heat sink 20. Thisfacilitates alignment of the semiconductor laser element 50 with theheat sink 20.

With such a disposition, turning the submount 40 upside down (that is,fixing the semiconductor laser element 50 to the submount 40 that isrotated by 180 degrees about the center of the second main surface 42)depending on whether the semiconductor laser element 50 has its opticalwaveguide region 55 positioned offset toward the lateral surface 53 (theright lateral surface when the light output surface 51 is the uppersurface, and hereinafter referred to as “the first lateral surface 53”)or toward the other lateral surface 54 (the left lateral surface whenthe light output surface 51 is the upper surface, and hereinafterreferred to as “the second lateral surface 54”) allows the opticalwaveguide region 55 to be disposed on or around the line A connectingbetween the midpoint of the upper edge and the midpoint of the loweredge of the second main surface 42. Accordingly, the submount 40 can beused for both the semiconductor laser elements 50 of two types differingfrom each other in the position of the optical waveguide region 55.

As used herein, the semiconductor laser elements of two types can bedefined as follows. For example, when the semiconductor laser elementsof two types are placed adjacent to each other on the right and leftsides having their respective light output surfaces directed upward,while they are different in whether the position of the opticalwaveguide region is offset toward the right side or toward the leftside, rotating one of the semiconductor laser element about its centerby 180 degrees sets the position of the optical waveguide region in thewhole semiconductor laser element identical to that in the othersemiconductor laser element. In other words, the semiconductor laserelements of two types are line symmetric to each other. Thus, in thecase where the submount 40 is turned upside down also, the position ofthe optical waveguide region of the semiconductor laser element issubstantially the same.

The distance between the light output part of the semiconductor laserelement 50 and the line A as seen in a front view is preferably 50 μm orsmaller, and the angle formed between the optical waveguide region 55and the line A is preferably 2° or smaller. Thus, the light output partof the semiconductor laser element 50 can be precisely aligned with theheat sink 20. Note that, the light output part of the semiconductorlaser element 50 is representatively disposed so as to be positioned atthe center of the semiconductor laser device 1 as seen in a plan view.Accordingly, preferably the heat sink 20 is disposed to achieve thefollowing: disposing the light output part of the semiconductor laserelement 50 so as to substantially match with the line that passesthrough the midpoint of the upper edge and the midpoint of the loweredge of the heat sink 20 as seen in a front view automatically positionsthe light output part of the semiconductor laser element 50 at thecenter of the semiconductor laser device 1 as seen in a plan view.

The first fixing part 43 is preferably elongated in one direction (thetop-bottom direction) for fixing the semiconductor laser element 50.This is because the optical waveguide region 55 has the shape elongatedin one direction, that is, the semiconductor laser element 50 includingthe optical waveguide region 55 has the shape elongated in onedirection.

The two second fixing parts 44 a, 44 b are disposed laterally relativeto the first fixing part 43 and respectively in the upper half regionand the lower half region of the second main surface 42. The side fromwhich the semiconductor laser element 50 emits laser light (the lightoutput surface 51 side) is the upper side, and the side opposite thereto(the light reflecting surface 52 side) is the lower side. The regionoccupying the upper half of the second main surface 42 is the upper halfregion, and the region occupying the lower half thereof is the lowerhalf region. The center of the second main surface 42 is a point ofintersection of the line A that passes through the midpoint of the upperedge and the midpoint of the lower edge of the second main surface 42and a line B that passes through the midpoint of the right edge and themidpoint of the left edge of the second main surface 42. Here, theregion being higher than the line B is the upper half region, and theregion being lower than the line B is the lower half region. Here, theterm “as seen in a front view” refers to viewing the second main surface42 of the submount 40 in the direction substantially perpendicular tothe second main surface 42.

In such a disposition, irrespective of whether the submount 40 isnormally oriented or turned upside down, the protective element 60 canbe fixed to upper one of the two second fixing parts 44 a, 44 b.Accordingly, the present embodiment can provide the semiconductor laserdevice 1 being reduced in size (reduced in length in the top-bottomdirection of the semiconductor laser device 1), and the semiconductorlaser device suitable for mounting the high-power semiconductor laserelement 50 with a greater cavity length (the length in the extendingdirection of the optical waveguide region 55). The reason thereof isexplained in the following.

As shown in FIGS. 3A to 4B, a collet 100 is used in performing diebonding or wire bonding of the semiconductor laser element 50 and theprotective element 60. The die bonding refers to disposing and fixingthe semiconductor laser element 50 and the protective element 60 torespective fixing parts, and the wire bonding refers to connecting thewires 70 to the semiconductor laser element 50 and the protectiveelement 60. In the die bonding, the semiconductor laser element 50 orthe protective element 60 is attached to the tip of the collet 100 undersuction, and carried to the bonding position. Further, in the wirebonding, the tip of the wire-bonding collet 100 that discharges the wireis pressed against the semiconductor laser element 50 or the protectiveelement 60. Therefore, the position of the semiconductor laser element50 and the protective element 60 must be in the range where contactbetween the collet 100 and the base 10 during such die bonding or wirebonding is prevented. In FIGS. 3A and 4A, the collet 100 contacts withthe base 10, so the collet 100 is allowed to move upward from a positionshown in FIGS. 3A and 4A.

Meanwhile, assuming that the second fixing part is provided just one innumber, when the submount 40 is turned upside down to be used for boththe semiconductor laser elements 50 differing from each other in theposition of the optical waveguide region 55, the distance between thesecond fixing part and the base 10 changes greatly. In this case, thesecond fixing part must be spaced apart from the base 10 so as to avoidcontact between the collet 100 and the base 10 irrespective of whetherthe submount 40 is normally oriented or turned upside down. When thesecond fixing part is disposed at the center of the submount 40, thedistance from the base 10 little changes by the submount 40 being turnedupside down. However, in this case also, the second fixing part must befully distanced from the base 10. In any of the cases, the second fixingpart being provided just one in number requires space above and belowthe second fixing part substantially equally, increasing the length ofthe submount 40 in the top-bottom direction.

In contrast thereto, in the disposition of the present embodiment, theprotective element 60 is fixed to upper one of the second fixing parts44 a, 44 b. Thus, irrespective of whether the submount 40 is normallyoriented or turned upside down, a great distance is reliably obtainedfrom the protective element 60 to the base 10, whereby contact betweenthe base 10 and the collet 100 is avoided. This eliminates the necessityof providing excessive space between the upper one of the second fixingparts 44 a, 44 b and the upper edge of the submount 40, and thusprevents an increase in length in the top-bottom direction of thesubmount 40. Accordingly, a reduction in size of the semiconductor laserdevice 1 (a reduction in length in the top-bottom direction of thesemiconductor laser device 1) is achieved.

Further, while the semiconductor laser element 50 of higher power can beobtained by increasing the cavity length (the length in the extendingdirection of the optical waveguide region 55), an increase in the cavitylength increases the length in the top-bottom direction of the submount40. However, in the disposition of the present embodiment, as has beendescribed above, an increase in length in the top-bottom direction ofthe submount 40 is prevented as compared to the case where the secondfixing part is provided just one in number. Accordingly, also in thecase where the semiconductor laser element 50 being greater in thecavity length is mounted, an increase in size of the semiconductor laserdevice 1 (an increase in length in the top-bottom direction of thesemiconductor laser device 1) can be prevented. Hence, the presentembodiment is suitable for mounting such a semiconductor laser element50.

In the case where the second main surface 42 is quadrangular beingelongated in the top-bottom direction, preferably, the distance d1between a first 42 a of two long edges of the second main surface 42 andthe first fixing part 43 is greater than the distance d2 between asecond 42 b of the two long edges and the first fixing part 43, and thesecond fixing parts 44 a, 44 b are disposed between the first fixingpart 43 and the first long edge 42 a. Thus, the region provided withneither the first fixing part 43 nor the second fixing parts 44 a, 44 bcan be reduced in size. Therefore, the second main surface 42 can bereduced in area, whereby the submount 40 can be reduced in size. Thedistance d2 between the other long edge and the first fixing part 43 is,for example, 10% to 80% as great as the distance d1 between the firstlong edge 42 a and the first fixing part 43. Further, the distance d2 ispreferably great enough to prevent the first fixing part 43 fromerroneously being cut in singulation of the submount 40, that is, forexample, the distance d2 is preferably 30 μm or greater.

The area of the first fixing part 43 is preferably at least as great asthe area of the semiconductor laser element 50 as seen in a front view.Similarly, the area of each of the second fixing parts 44 a, 44 b ispreferably at least as great as the area of the protective element 60 asseen in a front view. Normally, the protective element 60 is smaller insize than the semiconductor laser element 50, and therefore the area ofeach of the second fixing parts 44 a, 44 b is preferably smaller thanthe first fixing part 43. Thus, the second main surface 42 is reduced inarea within a range allowing the area of each of the fixing parts to begreat enough for the elements to be surely fixed, whereby the submount40 is reduced in size. Representatively, the total area of the twosecond fixing parts 44 a, 44 b is smaller than the area of the firstfixing part 43. The length of the first fixing part 43 (the length inthe top-bottom direction) is specifically greater than the length of thesemiconductor laser element 50. Further, an increase in length of thesubmount 40 necessitates an increase in length of the heat sink 20,resulting in an increase in length of the semiconductor laser device 1.Accordingly, the length of the first fixing part 43 is preferably equalto or smaller than the value obtained by adding about 100 μm to thelength of the semiconductor laser element 50. This suppresses anincrease in length of the semiconductor laser device 1.

(Semiconductor Laser Element 50)

The semiconductor laser element 50 may be a compound semiconductor suchas a Group III-V compound semiconductor. For example, the semiconductorlaser element 50 includes an active layer being a nitride semiconductorsuch as InGaN, GaN or the like. The semiconductor laser element 50includes, for example, on an electrically conductive or insulatingsubstrate, a semiconductor layered body which includes an n-typesemiconductor layer, an active layer, and a p-type semiconductor layer,and further includes an n-electrode electrically connected to the n-typesemiconductor layer, and a p-electrode electrically connected to thep-type semiconductor layer. As described above, the submount 40according to the present embodiment is suitable for mounting thesemiconductor laser element 50 with a great cavity length. The greatcavity length specifically means that the cavity length is at least halfas great as the length of the heat sink 20 (the length in the top-bottomdirection). Such a semiconductor laser element 50 with a great cavitylength is representatively high-power.

The semiconductor laser element 50 includes the light output surface 51and the light reflecting surface 52, and is fixed to the first fixingpart 43 so that the light output surface 51 is directed upward.Specifically, the semiconductor laser element 50 may be fixed with afixing layer made of Au nanoparticles, Ag nanoparticles, AuSn solder, asolder paste member or the like. The semiconductor laser element 50 mayhave its semiconductor layer fixed to the first fixing part 43(junction-down mounting), or may have its substrate fixed to the firstfixing part 43 (junction-up mounting). The optical waveguide region 55is a region elongated in one direction and connects between the lightoutput surface 51 and the light reflecting surface 52. The semiconductorlayered body may be provided with a ridge for current confinement andlight confinement. In this case, the portion where the ridge exists asseen in a front view is regarded as the optical waveguide region 55.

The semiconductor laser element 50 includes two lateral surfaces 53, 54that intersect with the light output surface 51. The lateral surfaces53, 54 are not in parallel to the first main surface 41 and the secondmain surface 42, and are representatively substantially perpendicular tothe first main surface 41 and the second main surface 42. The opticalwaveguide region 55 of the semiconductor laser element 50 is formed tobe offset toward one (in the present embodiment, the first lateralsurface 53) of the two lateral surfaces 53, 54. That is, the opticalwaveguide region 55 is disposed so as to exclude the line that passesthrough the midpoint of the upper edge (the edge formed by the lightoutput surface 51) and the midpoint of the lower edge (the edge formedby the light reflecting surface 52) as seen in a front view. Here, theterm “as seen in a front view” refers to viewing in the directionsubstantially perpendicular to the wire connected surface of thesemiconductor laser element 50. The wire connected surface is thesurface opposite to the surface fixed to the first fixing part 43.

The shape of the semiconductor laser element 50 as seen in a front viewis substantially quadrangular, for example.

As shown in FIGS. 1B and 1C, in the case where the optical waveguideregion 55 of the semiconductor laser element 50 is formed to be offsettoward the first lateral surface 53, the two second fixing parts 44 a,44 b are preferably disposed on the first lateral surface 53 side. Thisenables a reduction in size of the region provided with neither thefirst fixing part 43 nor the second fixing parts 44 a, 44 b when thefirst fixing part 43 is disposed such that the optical waveguide region55 is disposed on or around the line A connecting between the midpointof the upper edge and the midpoint of the lower edge of the second mainsurface 42. Thus, the second main surface 42 can be reduced in area,whereby the submount 40 can be reduced in size. The same holds true forthe case where the optical waveguide region 55 of the semiconductorlaser element 50 is formed to be offset toward the second lateralsurface 54. That is, in this case, the two second fixing parts 44 a, 44b are preferably formed on the second lateral surface 54 side.

The distance between the tip of the collet 100 brought into contact withthe semiconductor laser element 50 and the base 10, in other words, thedistance between the region on the semiconductor laser element 50 thatis brought into contact with the tip of the collet 100 and the base 10is the distance that avoids contact between the collet 100 and the base10, for example, about 760 μm to 1.0 mm. Accordingly, for example in thecase where the tip of the collet 100 is brought into contact with thecenter of an electrode of the semiconductor laser element 50, thedistance between the center of the electrode and the base 10 fallswithin such a range. Note that, the collet 100 normally has a taperedshape which becomes smaller toward the tip. Accordingly, the collet 100being brought into contact with the base 10 refers to a portion of thecollet 100, which portion is distanced from the tip and relativelythick, abutting on the base 10. Further, normally, the semiconductorlaser element 50 is greater in size than the tip of the collet 100.Therefore, the distance between the semiconductor laser element 50 andthe base 10 becomes smaller than the distance between the contactposition at the tip of the collet 100 and the base 10, unless thecontact position of the collet 100 is the lower end of the semiconductorlaser element 50. The smallest distance between the semiconductor laserelement 50 and the base 10 is, for example, from 100 μm to 300 μm.

(Protective Element 60)

The protective element 60 is a member for protecting the semiconductorlaser element 50 from electrical breakdown caused by surge current. Theprotective element 60 is connected in antiparallel to the semiconductorlaser element 50. In the case where a voltage is applied to thesemiconductor laser element 50 in the reverse direction, or an excessivevoltage is applied thereto in the forward direction, current is causedto pass through protective element 60 instead of the semiconductor laserelement 50. Thus, the protective element 60 prevents the semiconductorlaser device 1 from being damaged. The protective element 60 may be, forexample, a Zener diode. The Zener diode may be made of Si, GaAs and thelike.

The protective element 60 is fixed to the upper one of the two secondfixing parts 44 a, 44 b. Specifically, the protective element 60 may befixed with a fixing layer made of Au nanoparticles, Ag nanoparticles,AuSn solder, a solder paste member or the like.

As shown in FIGS. 4A and 4B, normally, the protective element 60 issmaller in size than the semiconductor laser element 50, and forexample, substantially as great as the tip of the collet 100.Accordingly, when the distance between the tip of the collet 100 beingbrought into contact with the protective element 60 and the base 10 isthe distance with which the collet 100 is not brought into contact withthe base 10, for example, about 760 μm or greater, the distance betweenthe protective element 60 and the base 10 also assumes the similarvalue. Further, in order to set the two second fixing parts 44 a, 44 bto be spaced apart, the distance between the protective element 60 andthe base 10 may be greater than the foregoing value, and may be, forexample, about 1.0 mm to 1.2 mm As described above, since the protectiveelement 60 is substantially as great as the tip of the collet 100, thedistance between the lower end of the protective element 60 and the base10 is, for example, about 1.0 mm at a minimum. Accordingly, theprotective element 60 is disposed such that its lower end is spacedapart from the base 10 farther than the lower end of the semiconductorlaser element 50.

Representatively, as shown in FIGS. 1B and 1C, the protective element 60is disposed to be higher than the wires 70 connected to thesemiconductor laser element 50.

In one semiconductor laser device 1, just a single protective element 60will suffice. That is, the protective element 60 should be fixed to justone of the two second fixing parts 44 a, 44 b (to just the upper secondfixing part 44 a), and other one of the second fixing parts 44 a, 44 b(the lower second fixing part 44 b) should be left unused.

(Wires 70)

The wire 70 connects between the semiconductor laser element 50 and atleast one of a plurality of lead electrodes 31, 32. Further, the wire 70connects between the protective element 60 and at least one of theplurality of lead electrodes 31, 32. In FIGS. 1B and 1C, the wire 70connects between the anode of the semiconductor laser element 50 and thesecond lead electrode 32. Further, the wire 70 connects between thecathode of the protective element 60 and the second lead electrode 32.The cathode of the semiconductor laser element 50 and the anode of theprotective element 60 are both electrically connected to an electricallyconductive layer 110 provided at the second main surface 42 of thesubmount 40 with an electrically conductive adhesive agent. Theelectrically conductive layer 110 is connected to the first leadelectrode 31 with the wire 70. Accordingly, the cathode of thesemiconductor laser element 50 and the anode of the protective element60 are both electrically connected to the first lead electrode 31. Aconnecting portion connecting between the electrically conductive layer110 and the wire 70 is positioned between the first fixing part 43 andthe other long edge of the submount 40 (the long edge on the side wherethe second fixing parts 44 a, 44 b are not disposed). Note that, whenthe protective element 60 and the like have their anode and cathode onthe identical surface, the electrodes should be directly connected tothe first lead electrode 31 and the second lead electrode 32 with thewires 70, respectively.

The wire 70 is a linear member made of metal such as Au, Ag or the like,and may have a diameter of about 10 μm to 50 μm.

The semiconductor laser element 50 and at least one of the plurality oflead electrodes 31, 32 may be connected to each other with a single wire70, or may be connected to each other with a plurality of wires 70.Similarly, the protective element 60 and at least one of the pluralityof lead electrodes 31, 32 may be connected to each other with a singlewire 70, or may be connected to each other with a plurality of wires 70.

(Others)

The semiconductor laser device 1 may further include a cap 80 that isdisposed to cover the semiconductor laser element 50 and the protectiveelement 60. The cap 80 may be made of, for example, Ni, Co, Fe, Ni—Fealloy, Kovar, brass or the like. The cap 80 may be bonded to the base 10by resistance welding or the like. Preferably, the bonding the cap 80 tothe base 10 airtightly seals the semiconductor laser element 50. Thus,the semiconductor laser element 50 is prevented from attracting dust dueto laser oscillation.

The cap 80 has an opening X at its upper surface, for allowing laserlight to transmit. In the present embodiment, as shown in FIG. 1E, theopening X is provided at the top of the cap 80 bonded to the base 10. Tothe opening X, a light-transmissive member 90 for extracting laser lightcan be provided. The light-transmissive member 90 may be made of, forexample, glass, sapphire, ceramic or the like. A functional membranethat selectively reflects light of a particular wavelength or aparticular angle may be provided at the surface of thelight-transmissive member 90. The light-transmissive member 90 maycontain a wavelength conversion member, a light diffusing member and thelike.

(Manufacturing Method)

In the following, a description will be given of a method ofmanufacturing the semiconductor laser device 1.

Firstly, the base 10, the heat sink 20, and a plurality of leadelectrodes 31, 32 are provided. Next, simultaneously with, before, orafter disposition of the submount 40 at the heat sink 20, thesemiconductor laser element 50 is disposed at the first fixing part 43.Simultaneously with, before, or after disposition of the semiconductorlaser element 50, the protective element 60 is disposed at the upper oneof the two second fixing parts 44 a, 44 b. Then, the protective element60 and one of the plurality of lead electrodes 31, 32 are connected toeach other with the wire 70.

The semiconductor laser element 50 used herein is selected from a groupconsisting of a semiconductor laser element in which the opticalwaveguide region 55 is offset toward one lateral surface (the firstlateral surface 53), and a semiconductor laser element in which theoptical waveguide region 55 is offset toward other lateral surface (thesecond lateral surface 54). The orientation of the submount 40 isdetermined based on the position of the optical waveguide region 55 ofthe selected semiconductor laser element 50. That is, the submount 40 isdisposed at the heat sink 20 as being oriented so that the opticalwaveguide region 55 of the semiconductor laser element 50 is disposed onor around the line A connecting between the midpoint of the upper edgeand the midpoint of the lower edge of the second main surface 42.

Note that, the first fixing part 43 is provided at the submount 40 inthe shape and position with which, irrespective of whether the opticalwaveguide region 55 is offset toward one lateral surface (the firstlateral surface 53) or toward the other lateral surface (the secondlateral surface 54), properly setting the upper edge and the lower edgeof the submount 40 disposes the optical waveguide region 55 on or aroundthe line A.

Through the foregoing operations, the semiconductor laser device 1 canbe manufactured.

As has been described above, according to the present embodiment,turning the submount 40 upside down depending on whether thesemiconductor laser element 50 has its optical waveguide region 55positioned offset toward the first lateral surface 53 or toward thesecond lateral surface 54 allows the optical waveguide region 55 to bedisposed on or around the line A connecting between the midpoint of theupper edge and the midpoint of the lower edge of the second main surface42. Accordingly, the submount 40 of a single type in which the fixingpart is formed at a unique position can be used for both thesemiconductor laser elements 50 differing from each other in theposition of the optical waveguide region 55. This prevents an increasein the number of types of the submount 40, making the inventory controlless troublesome.

Further, according to the present embodiment, irrespective of whetherthe submount 40 is normally oriented or turned upside down, theprotective element 60 can be fixed to the upper one of the second fixingparts 44 a, 44 b. Accordingly, in the case where the submount 40 of asingle type is used for both the semiconductor laser elements 50differing from each other in the position of the optical waveguideregion 55, an increase in length in the top-bottom direction of thesubmount 40 can be prevented. This achieves a reduction in size of thesemiconductor laser device 1 (a reduction in length in the top-bottomdirection of the semiconductor laser device 1), and it becomes possibleto provide the semiconductor laser device 1 reduced in size while beingequipped with the high-power semiconductor laser element 50 of a greatcavity length (the length in the extending direction of the opticalwaveguide region 55).

Semiconductor Laser Device 2 According to Second Embodiment

FIG. 2A is a schematic front view of a semiconductor laser device 2according to a second embodiment (in which the cap is not shown). FIG.2B is an enlarged view of a portion surrounded by a broken line in FIG.2A. FIG. 2C is a schematic front view of the submount 40 according tothe second embodiment. As shown in FIGS. 2A to 2C, in the secondembodiment, the optical waveguide region 55 of the semiconductor laserelement 50 is offset toward the opposite side relative to the firstembodiment. That is, the optical waveguide region 55 of thesemiconductor laser element 50 is offset toward the second lateralsurface 54. Therefore, as has been described above, the submount 40 isturned upside down. In this manner, using the submount 40, the opticalwaveguide region 55 can be disposed on or around the line A connectingbetween the midpoint of the upper edge and the midpoint of the loweredge of the second main surface 42, irrespective of whether thesemiconductor laser element 50 is of the type in which the opticalwaveguide region 55 is offset toward the first lateral surface 53 or ofthe type in which the optical waveguide region 55 is offset toward thesecond lateral surface 54.

Semiconductor Laser Device 3 According to Third Embodiment

FIG. 5A is a schematic top view of a semiconductor laser device 3according to a third embodiment (in which the cap is not shown). FIG. 5Bis a schematic cross-sectional view taken along line 5B-5B in FIG. 5A.FIG. 5C is a schematic cross-sectional view taken along line 5C-5C inFIG. 5A. FIG. 5D is an enlarged view of a portion surrounded by a brokenline in FIG. 5A. As shown in FIGS. 5A to 5D, the semiconductor laserdevice 3 includes a housing 120, the submount 40, the semiconductorlaser element 50, the protective element 60, and the wires 70. Themembers denoted by the reference characters identical to those in thefirst and second embodiments may be similarly structured as in the firstand second embodiments.

The housing 120 includes an insulating part 122 and a plurality ofwiring parts 124. The housing 120 includes a recess Y. The recess Y isdefined by a bottom surface Y1, and inner lateral surfaces Y2surrounding the bottom surface Y1. In the recess Y, part of the wiringparts 124 is exposed outside the insulating part 122.

The submount 40 includes the first main surface 41 and the second mainsurface 42. The first main surface 41 is fixed to the bottom surface Y1.The second main surface 42 includes the first fixing part 43 and the twosecond fixing parts 44 a, 44 b. The two second fixing parts 44 a, 44 bare disposed laterally relative to the first fixing part 43 andrespectively in the front half region and the rear half region of thesecond main surface 42. The side from which the semiconductor laserelement 50 emits laser light (the light output surface 51 side) is thefront side, and the side opposite thereto (the light reflecting surface52 side) is the rear side. The region occupying the front half of thesecond main surface 42 is the front half region, and the regionoccupying the rear half thereof is the rear half region.

The semiconductor laser element 50 includes the light output surface 51,the light reflecting surface 52, two lateral surfaces 53, 54intersecting the light output surface 51, and the optical waveguideregion 55. The optical waveguide region 55 is formed to be offset towardone of the two lateral surfaces 53, 54. The semiconductor laser element50 is fixed to the first fixing part 43 so that the light output surface51 is directed frontward and the optical waveguide region 55 is disposedon or around a line that passes through the midpoint of the front edgeand the midpoint of the rear edge of the second main surface 42 as seenin a top view. The term “as seen in a top view” refers to viewing thesecond main surface 42 of the submount 40 in the direction substantiallyperpendicular to the second main surface 42.

The protective element 60 is fixed to front one of the two second fixingparts 44 a, 44 b. The wire 70 connects between the protective element 60and one of a plurality of wiring parts 124.

The semiconductor laser device 3 includes a light reflecting member 130that is disposed at the bottom surface Y1, for example. The laser lightoutput from the semiconductor laser element 50 has its direction changedby the light reflecting member 130, and extracted from the opening X atthe cap 80.

The semiconductor laser device 3 having such a structure can exhibit theeffect similar to that exhibited by the semiconductor laser devices 1, 2according to the first and second embodiments.

It is to be understood that although the present invention has beendescribed with regard to preferred embodiments thereof, various otherembodiments and variants may occur to those skilled in the art, whichare within the scope and spirit of the invention, and such otherembodiments and variants are intended to be covered by the followingclaims.

What is claimed is:
 1. A semiconductor laser device comprising: ahousing comprising: a recess defined by a lower upward-facing surface, afirst upper upward-facing surface, a second upper upward-facing surface,and inner lateral surfaces, wherein the first and second upperupward-facing surfaces are formed inward of the inner lateral surfacesand above the lower upward-facing surface, and a plurality of wiringparts, the plurality of wiring parts including a first wiring partdisposed on the first upper upward-facing surface; a cap disposed on thehousing outside the recess; a submount comprising: a first main surfacefixed to the lower upward-facing surface of the recess, and a secondmain surface including a first fixing part and a second fixing part,wherein, in a plan view of the semiconductor laser device, the submountis disposed between the first upper upward-facing surface and the secondupper upward-facing surface; a semiconductor laser element including alight output surface, a first lateral surface intersecting the lightoutput surface, a second lateral surface intersecting the light outputsurface and an optical waveguide region, the semiconductor laser elementbeing fixed to the first fixing part of the submount; a protectiveelement fixed to the second fixing part of the submount; and a firstwire connecting the protective element and the first wiring part;wherein, in the plan view of the semiconductor laser device, a distancebetween the first lateral surface of the semiconductor laser element andthe first upper upward-facing surface is smaller than a distance betweenthe optical waveguide region and the first upper upward-facing surface;and wherein, in the plan view of the semiconductor laser device, adistance between the second lateral surface of the semiconductor laserelement and the second upper upward-facing surface is smaller than adistance between the optical waveguide region and the second upperupward-facing surface.
 2. The semiconductor laser device according toclaim 1, wherein, in the plan view of the semiconductor laser device,the optical waveguide region is disposed closer to the first lateralsurface of the semiconductor laser element than to the second lateralsurface of the semiconductor laser element.
 3. The semiconductor laserdevice according to claim 2, wherein, in the plan view of thesemiconductor laser device, a distance between the second fixing partand the first upper upward-facing surface is smaller than a distancebetween the first fixing part and the first upper upward-facing surface.4. The semiconductor laser device according to claim 2, furthercomprising: a second wire connecting the semiconductor laser element andthe first wiring part across the optical waveguide region.
 5. Thesemiconductor laser device according to claim 3, wherein: the pluralityof wiring parts includes a second wiring part disposed on the secondupper upward-facing surface; and the semiconductor laser device furthercomprises a third wire connecting the submount and the second wiringpart.
 6. The semiconductor laser device according to claim 1, furthercomprising: a light reflecting member disposed on the lowerupward-facing surface; wherein the plurality of wiring parts are locatedon both lateral sides of the light reflecting member, and are notlocated behind the light reflecting member in a direction from thesemiconductor laser device toward the light reflecting member.
 7. Thesemiconductor laser device according to claim 1, wherein the first andsecond upper upward-facing surfaces are above than the second mainsurface.